DE1462488A1 - Color television picture tubes - Google Patents

Description

IMpL-IiI ₉ . Ego"

Dr. Gertred Hawer tooo Me, _e k ... Pa.i ", August 22, 1966

Dipl.-liK). Gottfried Leismr Ern> br _ge r _S »rass. 19th

Lab

n: 13 15 10

—— ■ "—— 1A62488

our sign; C 2294

GOMPAGNIE FRAH ^ AISE DiI TELEVISION 1, rue d '^ njou

ASNISRES (Haute de Seine) / France

Color television tube

The invention "relates to three color n-color television picture tubes with a screen with fluorescent strips, which in the immediate vicinity of the screen and in front of it contains a grid which is applied to a potential which is smaller than the screen potential, and that with the screen a system of cylindrical lenses for each electron beam or, in the case of a cathode ray tube, for the single electron beam "forms.

As is known, the tubes of this type have a great advantage over the tubes, in front of the screen There is a shadowing mask, i.e. in the case of a screen with fluorescent strips, a wall that is only narrow, contains openings running parallel to the strips, the total area of the openings is very small

Lei / Ba fraction

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Represents fraction of the total area of the mask.

This 7 ₀ Advantage is in a high optical "efficiency and consequently in the possibility of a much larger brightness because" reaches hre wherein R ^ G-itter the vast majority of the electrons to the screen, while when the shading, the greater part of the Electrons are retained by the mask.

So while the tubes with shading mask from the In contrast, the tubes with a grating result from the above-mentioned point of view from fine wires every conceivable possibility with regard to the brightness.

The tubes with grids of the known type, however, have a due to the secondary emission of the grid weak point in terms of contrast.

The aim of the invention is to eliminate this

Disadvantage. .

According to the invention is a color television picture tube with at least one electron beam system, one Screen with fluorescent strips of different colors,

one

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a grid arranged in front of the screen in the vicinity thereof, which has openings, the direction of which coincides at least approximately with that of the fluorescent strips, the part of the grid surface grooved by the openings being at least of the same order of magnitude as the part occupied by the solid sections, devices To apply a positive potential Vg large value to the screen, which includes a "coating" covering the fluorescent strips, which is designed so that when the screen is scanned by the electron beam coming from the electron beam, an image of the grid can only be formed at a grid potential , which is smaller than i / _, and with means with which a potential V is effectively applied to the grid which is so smaller than Vg that the grid-Schira arrangement is a system of converging cylindrical lenses for the electron beam forms, where the potential Ύ_ is at least Vj / 4 , marked thereby et that the structure of the coating and the voltage V are such that V- is less than V_ and

V_ are less than 3V _v / 4,
g &

The invention is described below by way of example with reference to the drawing. Show in it:

]? ig.1 a very schematic partial sectional view of a stirrer known type to which the invention is applicable,

Figure 2 BAD

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Pig.2 the shape of the equipotential lines between the screen and the grid of the tube of Fig.1 and the paths of the Hectrons of an electron beam in the grid-screen space,

3 shows the secondary emission units in the grid-screen space,

4 shows a diagram for the representation of Widdington's law,

Fig. 5 shows the lack of purity caused by the lack of focusing of the point of light on the screen could be caused if no correction is provided with the help of a complex diaphragm limiting the width of the light point,

6 shows an embodiment of the invention in which a there is a complex diaphragm acting at the level of the grille,

FIG. 7 shows the geometric structure of the complex diaphragm from FIG. 6,

FIG. 8 shows a preferred embodiment of the one shown in FIG complex aperture,

9, 10 and 11 three embodiments of the invention, at which one bait combined the grating with a complex aperture

used

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is used, and

Fig.12 shows another embodiment of the invention, at »

which the complex screen is combined with the screen.

In all figures are the same! Dent with the same Provide letters or reference numbers "

For a clearer representation, the real size relationships had to be dispensed with.

The invention is exemplified below for the case a tube with a screen with vertical fluorescent strips and described with three beam systems, the screen having a regular structure, i.e. from exactly parallel Strips of the same width is formed.

In Fig.1 the left part of a stirrer is very schematically of this kind shown in a horizontal section.

Only the following ropes are shown inside the piston 1:

- the screen B, the one with alternating green, blue and red vertical Leuchtatoffetreifen is provided, with three successive strips each form a triple.

the

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The width of these strips, for example in the: Of the order of a third of a mm is in.der; Drawing compared to the dimensions of the piston very much exaggerated.

- In front of the screen a grid g made of thin wires that run parallel to the stripes and the triples, seen from a point lying on the tube axis, so that the grating is constant, but smaller than is the width of a tripod. The distance between the screen and the grille, for example in the order of magnitude of 2 cm is also shown exaggerated in the drawing.

- One of the three Eläfcronenstrahlsysteme, called "Rotstrahlsystem ¹¹ , Blaustrahlsyetem" and "Grünuitrahlsystem ¹ *" and each assigned to the fluorescent strips of the corresponding colors, the beam system shown in the drawing being the middle beam system 3, in the present case the red beam system.

- One of the elements 2 of the magnetic deflection arrangement.

In particular

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In particular, the conductive coating running around the circumference is not shown, which is often called ^H Ano * e ^H and covers the interior of the bulb between a vertical plane lying between a gate at the exit of the jet system and a vertical plane adjacent to the grid, just as little as the purity correction electrode. .which is preferably used in these tubes, or the convergence arrangement.

Briefly, let it be a possible type of operation of this kind per se known tubes repeatedly. .

The cathodes of the jet systems are essentially on Dimensions.

The screen S is even more put on a very high potential in the order of 20,000 Toit or even while the grid g on a much lower potential, for example, 5,000 volts is applied and the aforementioned A _n ode and the grosete Electrodes carrying the potential of the three beam systems are at potentials that correspond to the. Grid potential are the same or at least have the same order of magnitude.

The one emitted by the three electron beam systems Electron beams, the "red beam", the "blue beam" and the "green ray", which with the red, blue resp. green color value signals are intensity-modulated, becomes a with the help of the magnetic deflector

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common main deflection issued by that of the screen like scanned line by line in the pail of a black and white tube will.

These deflections take place along small arcs, the position of which depends on the deflection angle lie in the same vertical plane ("deflection ¹¹ ), which is indicated in Tig. 1 by the straight line xx ^{1. The} deflection center of the red beam is shown at 4, and the electron beam itself is symbolically shown in one of its positions by a dot-dash line.

The grid-screen arrangement provides for the electron beams a system of cylindrical lenses which, in a known manner, focuses the tin electron beams in the plane of the screen guaranteed under which the luminescent surface of the screen is to be understood.

In order for the picture to be satisfactory, two conditions must be met be fulfilled, namely the purity and the convergence. The first condition requires every electron beam is focused on a strip of the color assigned to it at any point in time, and the second condition requires

that

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that the three points of light are not far from each other, i.e. correspond to the same pixel.

Bs is balanced, the purity and the convergence at the same time in the middle of the track by moving the axles of the two lateral jet systems slight inclinations, in practice mostly in the order of magnitude of 1 °, against the Axis of the central beam system, which coincides with the tube axis, granted.

With a regularly set up umbrella like the one here it is generally impossible to determine the purity obtained in the center of the screen by such a static arrangement but the entire screen surface This follows in particular from the fact that the centers of deflection are not fixed points, and that the electron orbits of the electron beams between the Deflection centers on the screen are not straight.

A «known · measure to maintain the purity is that the screen is set up depending on the experimentally determined point of impact of the electron beams, which leads to screens with an irregular structure and very expensive production.

Another measure proposed earlier exists in that between the anode and the grid there is a correction electrode

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electrode is inserted through a between the critter, and the conductive coating applied to the anode on the bulb can be formed, both from the grid and from the The anode is insulated and connected to a potential that is changes depending on the main deflection movement.

Convergence is ensured, on the other hand, by a device that allows at least two of the three Eldtron Rays preferably immediately after hers To issue minor auxiliary deflections when exiting the jet systems, which depend on the main deflection movement.

In fig. 2 the middle rope of the Screen with red, blue and green fluorescent strips shown, the bits E, B and G- are designated. The ·· stripes are covered with a thin conductive layer 5, which allows the strips to be applied to the shield potential, but it is sufficiently thin that the incoming electrons reach the phosphors that form the strips leaves.

The illustration also shows the equipotential with dashed lines. lines between the screen and the grid as well as those from the red ray system able electron beam 9, which for a certain number of electron orbits is shown in full lines Elektrohenbahnen »iodine essentially parallel, and their

common

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gemeittsanie'Äicli-fcü.iig 'stekt immediately in front of the grid screen - space perpendicular to the grid. This vertical impingement on dae asks "comes from the fact that the mediator part of the screen is shown, but the parallelism of the electron paths is an approximation that is valid over the entire screen surface, if one takes into account the size relationships that arise from the electron-optical system of the electron beam system Focusing allows the diameter of the electron beam, "which at the exit" of the electron beam system hardly exceeds 3 "to 4 mm, immediately in front of the" grating up to about "^; pass mm; but since the Abstand.zwischen the outlet of the jet system and the "grid the Blektrbneisbahnion 'is, for example ⁷ 30"bis'ii O-a can' independently voti the deflection angle ^ "in the 'weBentrichen els' ¹ are considered in parallel. ■ .- - '<· ··. ·,

Finally, due to the potentiometric adjustment in the middle of the grid-screen hood, the GIe'ί Gi ^ i ^ r-Sbhirni ^ hbrdung forms a group of essentially identical converging 'cylindrical lenses (with each grid interval one Lens ^;

corresponds), these cylindrical lenses on the Beam systems facing away from the side have the same focal plane on points, which according to the state of the art essentially ' coincides with the screen surface * so that a largest '' Possibly £ onzenjfcra ^ fc lon the egg egg on the screen Taking into account the other parameters of the tube is guaranteed

Every_

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Each of these lenses in turn receives that of each of the three Beam systems coming electron beam in the form of a beam with essentially parallel electron cocks which it consequently focuses in a point of its focal plane. When the condition of purity is fulfilled, it will be found Focusing for each electron beam on a phosphor *, instead of a strip of the color assigned to it.

The focusing of the electron beams in the plane of the screen requires a ratio r = V./Vg of 1/4 if bit V _E denotes the screen potential and V_ denotes the grid potential

will. This gives:

⁷ E- V ^{= Y} E - ^{r <Y} E ^{= V} E ⁽¹ - ^r > with (1-r) in the order of 3/4.

¹ · f

Now, to ensure sufficient excitation of the phosphors, it is necessary to make Vg large, for example in the order of 20,000 volts.

From the above it follows that, according to the prior art, a considerable potential difference V ™ - Y ·

ij, g

comes, let for V _E = 20,000 volts and r = 1/4 has the value 15,000 volts, which, as will be shown, results in a serious disadvantage with regard to the secondary emission of the grid.

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j You can see the (hit · of a tube in terms of contrast « by the ratio never define C = lt ^ fh , where L ^ is the * saxioale brightness and L _{fi is} the bininal brightness, which a certain branch image generator is obtained at the same time on the referee with wise light (by applying appropriate voltages to the three beam systems) can.

A large value το η 0 is desirable, but the phenomena the secondary emission of the (litter prevent the achievement the usual number is the tubes with grids of a known type.

It is impossible to do these secondary emissions by doing this suppress that «an on the type of conductor wireβ des Öitters acts, since all conductive substances result in a secondary emission, if also in different degrees, and Tersottiedene ÜserlefTUBeen i * other iie Vahl 4er used Fabrics eesohr «it» e. «

It is clear tMMSkt, tos »the A» f deep fen der ankoseeaien / llektroa + astsakle * nioat aur su a secuaiäreaission of the »itter ·» s «a * erm auoh wm a secuni & reaission des Sehires fttkrt,« 1 « in the « Ivi · · "Awh bei" en tubes old Absohattang * - _r "aske, 4e4ooh is much more critical than IefcasAareeiesien In iitters hinsiohtlioh their eytiaofce · Ioasea.ueosea how oaohstehead is explained.

\? BADOfNNAl

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Fig. 3 shows the secondary chemistry phenomena in the lattice Sohirm tree.

Iq smaller MaBetab Bind again the middle rope dea Screens E, the corresponding part of the sitter g and the red beam 9 shown in this manner is shown (where the hatches have no physical meaning).

The arrows 7 drawn in rolling lines represent the initial center of the orbits of the electrons, which are caused by the electrons of the ankosende electron beam through secandary dissolution have been torn from the leading order. Baoh repulsion Secondary electrons fall on the grid Line of the Soire: »urüok.

Others reieet * he ankolmeaa · liektroneastrahl au · de «eitter Sekua« ftrelefetroaea _t Tea iaaen Title «ftf * ea Stair · eatlang llektroaeneaaae» iaruokfaliea, tie la weseatlieheB vertical »vl · Schira rerlaufen,« 1 · is.

optieohen Ausvirkuagen these SekuaAareBissieasersohelaaagen kOaaen aar uater lerttoksiohtiguog the general lere) aar BaergiSTteiluag «er τοα a substance aageeenen secaadarelectrons evaluate.

Sat

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The large mass of these secondary electrons, "for example about 80% in the case of a primary electron beam of 20 Electron volts, is concentrated in an energy band, the upper limit of which is on the order of 30 to 50 ToIt. These electrons are called "slow" electrons.

A much smaller one, but not absolutely negligible Fraction of ^^ kundaryJUe-lc-tronen: exhibits a; - energy in the; The order of magnitude of the energy dex ^ primary electrons. These Electrons are called "fast" electrons.

The rest is distributed between these two energy bands. These electrons are called "emit electrons".

On the other hand, the law of WMditrgton says that the electrons which pass through a layer of a given composition and thickness _{suffer an energy loss V ^ - V 2} in electrons v3, t, ideji, dex ^ by the following equation

is given: ,,,,. ^, ., - ^ ■> /. ■, ..-. - ■■ '" '

"t a 'χ

r 2
V ₁ e. V ₁

Therein: T _{1 is} the energy of the electron at the entrance of the layer

T ₂ the exit energy of the electron.; e ₍ the, charge of the electron 3c, the thickness of the layer

Q ₁ , a numerical constant that depends on the type of layer and the binding system. '

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It is worth remembering here that one of the speed Zero electron accelerated with the help of a voltage 7 has a kinetic energy mv / V, where m is the mass and ν are the speed of the electron, which is equal to V electron volts. To simplify the expression, from now on to be said that an electron has a "velocity of V YoIt" instead of saying that its velocity is ν is so large that mv / 2 = V electron volts.

Pig.4 shows Widdington's law for the case that χ is dimensioned in such a way that the right half of equation (1) _{becomes zero for V 1} = 10,000 volts. The entry velocity V ^ of the electron is plotted on the abscissa , and on the ordinate the ratio Vp / V of the exit velocity to the entry velocity.

In general, it is always possible to set a threshold T ¹ .

to determine which is called the excitation threshold and is sufficiently small that Vp goes to zero or something

it becomes small that perpendicular - or with any angle of incidence - ^{electrons arriving at a layer 5 at each speed T 1} , the luminescent substances beyond the

Layer can not excite.

Venn

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If under these conditions the secondary electrons of the The screen fall back on the screen, which is for everyone who is slow Electrons will be the case, they fall on it with a Velocity components perpendicular to the screen, which are of the same size and directed in opposite directions like the one they showed when they were torn from the screen.

In general, it is sufficient to coat the screen without any special precautions to absorb the slow electrons of low energy so that they cannot reach the phosphor strips. The fast electrons and the middle electrons can _{pass through the grid to the extent that their component Y Q of} the initial velocity, which is perpendicular to the screen, exceeds the potential difference Vg - Y. In this regard, it is expedient to give the aforementioned envelope anode "a potential which is slightly greater than the grid potential in order to capture these electrons.

The rest of the fast electrons and medium electrons may or may not excite the fluorescent strips, depending on whether their speed component T is greater or less than

.V ₁ lot.

i
Thus, as for the secondary emission of the screen, the elimination of the slow electrons can be easily obtained, and only the medium and fast electrons can be harmful.

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This also applies to the secondary emission of the grating. The "slow" electrons, which are also the predominant ones here Plural there? Form secondary electrons, namely are perpendicular to the screen by the voltage V-g-V of the lattice screen space accelerates before they fall on the screen.

The covers normally used for the screen, designed to give a very satisfactory excitement of the screen is ensured by the primary electrons accelerated perpendicular to the screen by a voltage T-g is not sufficient to absorb the secondary electrons with a velocity component perpendicular to the screen in the order of magnitude of 3Vg / 4.

For this reason, the great majority of secondary electrons excite of the grid the fluorescent strips. In addition, that a large number of them have electron orbits that run essentially perpendicular to the screen and cause an image of the grid on this screen, which is particularly disturbing is.

According to the invention, a conductive coating of this type and a potential difference V ₁₁₁ -V therefrom are used

Üj g

Great that no image of the grid is noticeable on the screen is, by the rest of the primary electrons of the electron beam.

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beam is really excited.

Theoretically, this leads to the condition: ^V E - ^T g < ^T 'i < ^V E

where V -j ^ ie still calculated the law of Widdington " Threshold is

This is because it would appear that the above statement is too summary of the phenomena that occur, and that, taking into account the experimental results, the application of the invention consists in that the coating, the potential Y and the potential V _E are dimensioned in such a way that no image of the grid appears on the screen when it is normally illuminated with the aid of the electron beam. For a given coating and a given screen voltage Vg, one can easily determine experimentally the aforementioned value V (in the manner

that an image of the lattice is only formed at a lattice potential that is smaller than V),

Β »*

This generally leads to the use of a ratio r = V / V _B »which is greater than the value r = 1/4, which ensures the focusing of the electron beam arriving at the grating on the screen.

on

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In any case, the ratio r must not become too large and must remain smaller than 3/4, otherwise the focusing; ^: ι. becomes too weak for proper operation of the tube in the grid-screen space.

Experience shows that, for example, a voltage V- ^ in the order of magnitude of 20,000 ToIt or more and assume a ratio r on the order of 0.30 to 0.35 and that formed by the conductive coating The obstacle can be dimensioned in such a way that a correct excitation of the screen is obtained by the primary electron beams, without an image of the grating being noticeable, and without the defocusing becoming so great that it is noticeable The result is a lack of purity of the tube with fluorescent strips in the order of magnitude of 0.3 mm, although of course it is assumed that the electron optics of the tube are connected these operating conditions are adapted.

In addition, one then finds that the disappearance of the image of the grid with an enormous improvement in the contrast connected, which, among other things, is likely to be due to better absorption of the medium falling on the screen or fast secondary electrons is due to a coating that covers the electrons represents a much larger obstacle than the obstacle formed by the usual coatings.

Regarding

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With regard to the formation of the coating, it is clear that if it is homogeneous, Y the smaller and that before

go

The thickness of the coating, the greater the potential V _Eo . Technologically speaking, a problem arises because from a certain thickness of the layer used, which consists for example of aluminum, the coating tends to peel off. To achieve a coating with a high excitation threshold, several superimposed layers are preferably used. An advantageous solution is that an aluminum layer is used, which is covered with a graphite layer, which also gives the door part that the secondary emission of the screen is reduced.

One can commit to more stringent conditions in the following manner.

The lower limit Y _{Eo of} the screen potential is determined for which the scanning raster is noticeable on the screen surface when the screen is scanned with the electron beam coming from one of the beam systems, and the tube works with potentials V ₁ , and T ■, for which V applies ₁ , - V <V The coating is preferably dimensioned for a given value of V ™ such that T is at least equal to T ₇ , / 4.

BO ^Δ

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Other solutions are possible. Using a Ratio r which is considerably larger than 1/4, for example r = 1/2, can, however, for a given Width of the fluorescent strips lead to the result that the width of the light point on the screen is the same If the stripe exceeds, this deficiency can be remedied with the help of a diaphragm, as described below will.

One can use a complex diaphragm 10, as shown in Mg.6, where again the middle part of the Screen E and the grid g are shown, as well as the electron beam 9, its hatched temporal parts be held back by the complex aperture. The panel is, for example, 1 cm in front of the grille and is attached to the same potential as this one.

The complex aperture consists of massive vertical strips 11, which are impermeable to the electrons and separated from each other by slots running parallel to the strips are so that the part 90 of the electron beam 9 is retained after the focusing or rather the partial focusing due to the grid-screen arrangement, parts of the light point that are part of the light are created over the red Stripes went out.

¹ "·. You

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Me massive strips 11 are arranged so that they the Mask the electron beam in the specified manner regardless of the deflection angle, as shown in Pig. 7, which corresponds to the representation of Mg.6, but for a different area of the screen in which the electron beam no longer hits the grid perpendicularly Lines indicate the width in the end portion of the electron beam in the absence of the aperture.

In general, if the complex aperture provides the purity for the Restoring the electron beam of the medium beam system, it also fulfills the same task in a satisfactory manner for the other two electron beams. However, one can So choose a certain factor of safety in determining the width of the massive strip in this regard any danger is avoided.

With a grid of constant pitch one comes to one complex aperture with essentially constant pitch.

The following should be noted: If the membrane 10 and the grid g are placed at the same potential V, forms Finally, the aperture is the actual grille, and in particular it is ultimately the aperture that essentially would produce an image on the screen if the screen coating and the potentials used were not appropriate of the invention would be measured.

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One can therefore leave out the grid g. However, this can.

can also be retained as an auxiliary element by giving it a potential V which is slightly smaller than that at the diaphragm applied potential is V_. It is easy to see that these measures with regard to the effects of secondary emissions is cheap.

"Regardless of whether the grid is retained or not, it should be noted that the suppressed portion of the electron beam falling on the sitter diaphragm 10, since this one has a circular cross-section, calculated as a percentage of the surface its cross-section eliminated as a result of the diaphragm is much smaller than the percentage reduction in its Width is. And furthermore the electron beam is denser in its middle rope than in its Uafag part (da the distribution of electrons over a diameter of the electron beam essentially follows the Gaussian curve, with the maximum space on the axis) is the percentage reduction in the number of electrons reaching the screen even smaller.

Pig.θ shows a preferred one in front view and in section Aitführungform the grille screen 10. It consists of one Mesh 10 made of very thin wires, and the solid parts 11 of the screen, are then obtained by that, for example, a suitable substance such as carbon, silver or aluminum is applied by a photographic process will.

gig.9

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Pig.9, 10 and 11 show three further embodiments of the Cover.

In the first version (Pig. 9) the wires of the Lattice so thickened that it is the unwanted part hold back the electron beam.

However, this solution is not optimal (risk of blurred points of light). Fig. 10 shows another embodiment, in which a screen effect is given to each grid interval by the fact that these intervals are not limited by a single wire, but by a group of three wires, whose axes lie in one plane, and whose Cross-sections tangent to each other. The diameters of the two side wires of each group are preferably smaller than that of the middle wire, which would be an excellent measure for preventing vibrations of the guitar, Since the resonance frequencies of the side wires and the middle wire are then different, »in can choose the Durohmesser in a ratio of 7: 8, for example. The Durohmessex ratio is much greater in the newspaper. the Durohmeters can also be different for all three wires.

The complex membrane of 7ig.11 is used again Groups of three wires of unequal diameter, but whose axes form the edges of a triangular prism. the

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technological execution is simpler than with the complex aperture of Pig.10.

fig. 12 finally shows an embodiment of the invention, in which the aperture has an artificial texture in the sense that it does not correspond to the width of the electron beam but only the width of the active wire of the electron beam limited.

Each triple fluorescent strip is widthwise reduced and surrounded by two dead strips 23 in which the faceplate is not covered with phosphors; it may preferably be covered with charcoal, for example. The dead Strips are of such a width that they cover those portions of the screen in which the lateral Parts of two electron beams are superimposed, like this that the active parts of the three electron beams cannot penetrate each other and each electron beam only excites the strip with the color to which it is assigned.

In I ¹ Ig.12 the dead stripes have a width which is somewhat larger than the absolute minimum (at which the red ray in the plane of the drawing on the screen would cover the middle red stripe R and the two neighboring dead stripes). This makes it easier to achieve purity with a larger manufacturing

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and / or adjustment tolerance.

It can, of course, be the width of the dead Reduce stripes to the minimum, or, on the contrary, use wider dead stripes around the aforementioned The advantage in terms of purity still needs to be strengthened, although the width of the strips of light material is of course still sufficient must stay.

The invention is of course suitable for all color television tubes η with one or more beam systems, which contain a screen with vertical or non-vertical strips of light, and those near the A grating is arranged on the screen, which on its own or not and in conjunction with the screen results in a focusing effect. When it comes to using color control grids variable potential is to be below V.

understand medium potential.

In the special case ^ that the purity does not signal purity correction, but with the help of a screen and a Lattice of irregular construction is obtained, the structure of the complex diaphragm must obviously have this Take into account irregularities.

The training of casing pipes according to the invention has it allows with a test pattern consisting of two black and white sections, which are the right half or

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cover the left half of the screen, a contrast of
100 or more (versus about 10 for a conventional
Tube) to reach between two points, respectively
3 cm from the theoretical black and white dividing line, and a contrast of 250 or more (compared to about 20 with a conventional tube) between two points that are 10 cm away from this dividing line.

Sponsorship claims

809812/0885

Claims (11)

Color television picture tube with at least one electron beam system, a screen with fluorescent strips of different colors, a grid arranged in front of the screen in the vicinity thereof, which has openings whose direction at least approximately coincides with that of the fluorescent strips, the rope of the grid surface occupied by the openings being at least the same Grössenordnang as the space occupied by the solid portions! part, means for applying a positive potential Vg large value to the screen, for which purpose a phosphor strips of covering coating is one that is adapted so that when scanning the screen by the electron beam sys tee coming through the Electron beam an image of the lattice can only be formed at a lattice potential that is less than V, and with devices with which a potential V is effectively applied to the lattice, which is so smaller than Y-g that the grid-screen arrangement a system of converging cylindrical lenses for the electron beam, the potential Y being at least equal to Vg / 4, characterized in that the structure of the coating and the voltage Y are such that V is less than Y and Y is less than 3Y _E / 4. 809812/0885 2. Color television picture tube according to claim 1, characterized in that the difference Vg -V is smaller than V _EQ when Vg _{0 is} the minimum voltage that is to be applied to the screen so that the deflection raster when scanning the screen provided with the coating the electron beam becomes noticeable. 3. Color television picture tube according to claim 2, characterized in that the structure of the coating and the voltage Vg are such that Vg _{0 is} at least equal to V _E / 4. 4. Color television picture tube according to one of the preceding claims, characterized in that the coating consists of two or more superimposed layers is formed. 5. Parbfernsehbildröhre according to claim 3 »characterized in that that the coating contains an aluminum layer which is covered with a graphite layer. 6. Color television picture tube according to one of the preceding claims, characterized by means for reducing the width of the spot of the electron beam perpendicular to the screen to the direction of the fluorescent strips. 7. Parb television picture tube according to claim 6, characterized in that that the facilities are contained in the grid. 809812/0885 8. iarbernsehbildröhre according to claim 7, characterized in that that each grid interval is limited by two groups of three wires that are tangent to each other in pairs. 9. "Color television picture tube according to claim 8, characterized in that that the axes of the three wires in each group form the edges of a triangular prism. 10. Parbfernsehbildrühre according to claim 9, characterized in that that the diameters of the three wires of each group for all three, wires or for one wire on the one hand and the two other wires on the other hand are different. 11. Parb television picture tube according to claim 6, characterized in that that the devices are not the width of the electron beam (s), but the width of their active one Partly delimit and are made up of non-luminescent strips interposed between the successive Fluorescent strips are inserted.